Description: The Upper Mystic Lake suffers from both chronic and acute contamination by arsenic and other heavy metals. Predictions require an understanding of the physical, biological and chemical processes determining the fate of the arsenic within the lake. Four major pathways influencing arsenic concentration will be examined in this study: transport through and trapping in shallow forebays; initial transport to lake sediments; subsequent and repeated remobilization from lake sediment; and finally, vertical transport to and within the surface waters. Intensive field measurement will be used to characterize both the temporal and spatial variability of these processes. Measurement will focus on 1) arsenic speciation, concentration and soluble vs. particulate fraction; 2)particulate suspension and deposition; and 3)the mean and turbulent flow fields. The specific goal will be to produce a conceptual model of the physical, biological and chemical processes active in determining the arsenic distribution in the system.